1. Field of the Invention
This invention relates to wireless communication systems and methods; and more particularly, to a system and related method of optimizing signal quality for a plurality of devices linked to a WiFi network.
2. Description of the Related Art
Mobile devices such as laptops, tablets, personal digital assistants, cellular phones and smart phones, as well as fixed devices such as desktops, workstations, printers, etc., can be connected to wireless local area network (WLAN) links through an access point such as a router. Modern WLANs are adapted to operate in accordance with the IEEE 802.11 standards for communication in the 2.4, 3.6 and 5 GHz frequency bands. WiFi is defined as WLAN products that are based on the IEEE 802.11 standards. The term WiFi is often used as a synonym for WLAN. Implementations of WLANs range from small in-home or in-office networks to large campus-sized or airport-sized networks, and have become popular due to ease of installation and low cost or often free access. However, WiFi networks generally have a limited range. For example, an access point using IEEE 802.11b or 802.11g may have a range of approximately 120 ft indoors. The range varies with frequency band. For example, WiFi in the 2.4 GHz band has a slightly wider range than WiFi in the 5 GHz band which is used by 802.11a and optionally by 802.11n. Therefore, the WiFi coverage over a large area requires a group of access points with overlapping ranges.
WLAN internal roaming involves a situation wherein a wireless device moves the connection from one access point to another within a WiFi network because the signal strength from the original access point gets too weak. The wireless device may include an algorithm to periodically monitor the presence of alternative access points, which may provide a better connection, and to re-associate itself with an access point having a stronger signal. However, due to the complex nature of radio propagation, it is difficult to predict WiFi signal strength for a given area in relation to a transmitter. In many instances, the line of sight between a transmitter and a receiver involved in the communication becomes blocked or shadowed with obstacles such as walls, trees and other objects. Each signal bounce may introduce phase shifts, time delays, attenuations and distortions, which ultimately interfere at the receiving antenna. Destructive interference in the wireless link is problematic and results in degradation of device performance. A signal quality metric is often used to assess the quality of signals. Examples of such quality metrics include signal-to-noise ratio (SNR), signal to interference-plus-noise ratio (SINR), receive signal strength indicator (RSSI), bit error rate (BER) and various other metrics, which are called channel quality indicators (CQI).
Increasing the number of access points in a WiFi network generally provides network redundancy and support for fast roaming by defining smaller cells. However, WiFi connections may be disrupted and/or internet speed may be lowered due to interference by having too many devices in the same area connected to one access point. A wireless device typically has one antenna with one mode (i.e., one radiation pattern), and the access point connected to the device is not capable of modifying the radiation pattern of the antenna of the device. This situation leads to a sub-optimal traffic, wherein one access point may be overloaded while another is underloaded. Therefore, quality of service (QOS) offered to the users is not optimized in this scenario.